> there's no "middleman" unless you are using an e-mail forwarding service

Each time an e-mail passes through an e-mail service that service is required to add a "Received" header to the e-mail. So you can easily check out of your real e-mails to see if you are using any middleman or not. The first e-mail I opened looks like this:

    Received: from exdb06.ug.kth.se (192.168.32.116) by exdb02.ug.kth.se
    Received: from mx5.kth.se (130.237.32.10) by exdb06.ug.kth.se (192.168.32.116)
    Received: from mx5.kth.se (localhost [127.0.0.1])
    Received: from mx5.kth.se ([127.0.0.1])
    Received: from buffalo.birch.relay.mailchannels.net (buffalo.birch.relay.mailchannels.net [23.83.209.24])
    Received: from relay.mailchannels.net (localhost [127.0.0.1])
    Received: from uscentral412.accountservergroup.com (ip-10-27-139-41.us-west-2.compute.internal [10.27.139.41])
    Received: from uscentral412.accountservergroup.com (uscentral412.accountservergroup.com [10.102.194.57])
    Received: from friendly by uscentral412.accountservergroup.com with local (Exim 4.87)